Wiping the nozzle face of a printhead is an effective way of removing paper dust, ink floods, dried ink or other contaminants. However, a pagewidth printhead is difficult to wipe. While pagewidth printers with nozzle face wipers exist, the wiping mechanism is relatively slow and or complicated. Currently available pagewidth printers have several printhead ICs spaced apart from each other in the media feed direction. It is impractical for a single wiper to clean all the printhead ICs, so each printhead ICs is wiped individually. Furthermore, the wipers move transverse to the media feed direction. This is to avoid colour mixing between nozzles of different colour. The rows of nozzles for each colour extend across the printhead ICs in a direction transverse to the media feed direction. Wiping along the row of nozzles minimises the risk of contaminating in one nozzle with ink of a different colour. However, as the printhead ICs are elongate and extend transverse to feed direction, the wiper must travel the entire length to clean all the nozzles. In light of this, the mechanism that actuates the separate wipers for each printhead ICs is complex, occupying a relatively large space and consuming a significant amount of time to complete each wiping operation.
The Applicant has developed a printhead maintenance facility that can wipe the nozzle face of a pagewidth printhead in a direction parallel to the media feed direction. The ordinary worker will appreciate that the wiping member needs only travel short distance to wipe all nozzles when moving parallel to the feed direction. Consequently the wiping operation is completed much more quickly. To avoid colour mixing, the nozzles can eject ink to a blotter immediately after being wiped. As the wiping operation is completed quickly, any contaminating ink in the nozzle of different colour has very little time to diffuse into the nozzle and its associated nozzle chamber before the nozzles are fired and the ink purged.
Wiping the nozzle face of pagewidth printhead with a single long contact surface can be ineffective. Inconsistent contact pressure between the wiping surface and the nozzle face can cause the contact pressure to be insufficient or non-existent in some areas. One of the reasons that the contact pressure will vary is inaccurate movement of the wiper surface relative to the nozzle face. If the support structure for the wiping surface is not completely parallel to the nozzle face over the entire length of travel during the wiping operation, there will be areas of low contact pressure which may not be properly cleaned. Furthermore any inconsistencies in the contact pressure can cause particular wiping surfaces, such as a wiper blade, to buckle and lift from the nozzle face. It is possible to avoid this by positioning the wiper blade so that it is angled relative to feed wiping direction and the printhead nozzle face. In this way, only one portion of the wiper blade contacts the nozzle face at any time during the wiping operation. This keeps the contact pressure more uniform but it requires the wiper blade to travel further for each wiping operation. As discussed above, inaccuracies in the movement of wiper surface relative to the nozzle face source of insufficient contact pressure. Increasing the length of wiper travel only increases the risk of such inaccuracies.